The present invention relates generally to a response waveform synthesis method and apparatus for synthesizing a time-axial impulse response waveform on the basis of acoustic characteristics in the frequency domain, an acoustic-designing assistance apparatus and method using the response waveform synthesis method, and a storage medium storing an acoustic-designing assistance program.
For installation of a speaker system in a hall, event site or other room (or acoustic facility), it has heretofore been conventional for an audio engineer or designer to select a suitable speaker system on the basis of a shape, size, etc. of the room (or acoustic facility) and then design a position and orientation in which the selected speaker system is to be installed and equalizer characteristics, etc. of the speaker system to be installed.
Because the designing work requires skill and cumbersome calculations, there have so far been proposed various acoustic-designing assistance apparatus and programs, for example, in Japanese Patent Application Laid-open Publication Nos. 2002-366162, 2003-16138, HEI-09-149500 and 2005-49688 (which will hereinafter be referred to as patent literatures 1, 2, 3 and 4, respectively). With the acoustic-designing assistance apparatus and programs, it is desirable that acoustic characteristics in a surface (hereinafter referred to as “speaker-sound receiving surface” or “sound receiving surface”) where seats or the like are located and which receives sounds from speakers to be installed an acoustic hall or other room (or acoustic facility) be visually displayed in advance on a display device, on the basis of characteristics of a selected speaker system, so that the acoustic characteristics of the selected speaker system can be simulated so as to assist in selection of the speaker system before audio equipment, such as a speaker system, is carried into the room (i.e., actual acoustic space), such as an acoustic hall. Further, it is desirable that, even after installation, in the room, of the selected speaker system, such an acoustic-designing assistance apparatus and program be used to simulate acoustic adjustment states of the system so that the acoustic adjustment states can be reflected in acoustic adjustment of the system.
The aforementioned No. 2002-366162 publication (i.e., patent literature 1) discloses obtaining in advance data of impulse responses of various positions around each speaker and automatically calculating sound image localization parameters of a sound receiving surface on the basis of the obtained impulse response data. According to the disclosure in this literature, templates of the impulse responses are prestored by the impulse responses being subjected to FFT (Fast Fourier Transformation). Patent literature 2 identified above discloses an acoustic-system-designing assistance apparatus which automatizes equipment selection and designing work using a GUI (Graphical User Interface). Patent literature 3 identified above discloses an apparatus which automatically calculates desired sound image localization parameters. Further, Patent literature 4 identified above discloses an acoustic adjustment apparatus which automatically adjusts acoustic frequency characteristics, in a short period of time, using characteristic data of differences between sound signals output from speakers and sound signals picked up by a microphone in an actual site or room.
Moreover, acoustic-designing assistance programs arranged in the following manner are in practical use today. Namely, although their application is limited to a speaker system of a planar or two-dimensional line array type, each of such acoustic-designing assistance programs calculates a necessary number of speakers and orientation, level balance, equalizer (EQ) parameters and delay parameters of each of the speakers for a predetermined sound receiving area of a sound receiving surface, by inputting thereto a sectional shape of an acoustic room, such as a music hall or the like.
With the aforementioned conventionally-known acoustic-designing assistance apparatus, there has been a demand for a function for simulating acoustic characteristics of sounds from speakers when the sounds have been received at a given sound receiving point (e.g., seat) and permitting test-listening of the simulated sounds so as to check in advance what kinds of sounds can be heard at the sound receiving point.
In many of the aforementioned conventionally-known acoustic-designing assistance apparatus, analysis of frequency characteristics is performed by dividing a frequency range of an audible sound into a plurality of partial bands and then performing FFT analyses on the partial frequency bands with the number of sampling points differing among the partial frequency bands, to allow frequency resolution to become finer in order of lowering frequencies of the partial bands. However, if frequency characteristics obtained from the plurality of partial frequency bands are merely added together after being subjected to inverse FFT transformation independently of each other, there would arise discontinuous or discrete points in the frequency characteristics, which tends to cause unwanted noise and unnatural sound.